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Growth of radiation uses in medicine
How big, how fast and why? ….Is it justified ?
G. William Morgan LectureHealth Physics Society
Oakland, CA, January 29,2008
Fred A. Mettler Jr. M.D., M.P.H.
Chief, Radiology & Nuclear Medicine
New Mexico Federal Regional Medical Center
Professor, University of New Mexico
Albuquerque, New Mexico
NCRP SC 6-2 Radiation exposure of U.S. population 2006
Medical 1980 Occupational
Natural Technologically enhanced
Report probably to be published in 2008
1987
Medical Subgroup SC 6-2
• B. Thomadsen, Chairman, Univ of Wisc.• M. Bhargavan, American College of Radiology• D. Gilley, State of Florida• J. Gray DIQUAD, LLC• J. Lipoti, State of New Jersey• M. Mahesh, Johns Hopkins Univ.• J. McCrohan, U.S. F.D.A.• F. Mettler, Univ of New Mexico VA• T. Yoshizumi Duke Univ.
• M. Rosenstein Scientific NCRP Consultant• K. Kase Stanford SC 6-2 Chair
Assumptions and Issues
• Benefit exceeds risk (maybe)
• RBE = 1 (…..or more)
• Weighting Factors: Used ICRP 60 (1990). Past reports used older ICRP 26 (1977) and new factors are suggested.
(not a big deal for most exams)
Major changes in imaging over the last decade that involve substantial radiation doses
• New uses of CT– Clinical
– Screening– CT combined with other procedures
• Cardiac nuclear medicine• Digital radiography• Increasing use of radiation by non-radiologists
Preliminary Results (U.S. 2006)
NA
5
9
18
3
64
%
--
26
0.7
50
13
10
%
-- NA1 million ptsRadiotherapy
0.8231,00018 millionNuclear Medicine
Dental
0.016,00034 millionMammography
1.5440,00067 millionCT
0.4112,00013 millionInterventional
0.388,300244 millionRadiography
Per capita (mSv)
Collective dose(Person-Sv)
Number
procedures
Total x-ray + NM = ~ 375 million ~ 880,000 ~ 3.0
Preliminary Results for Radiography (2006)
3.83,5400.41.2IVP
5.55,2000.20.65Barium enema
25.624,1501.44Upper GI
19.718,6006.518Spine
0.217420.557Extremities
~94,000~278Total
6.35,98412.234Mammography
14.013,1567.220Pelvis/Hips
11.110,4755.414.9Abdomen
13.312,58546126Chest
0.44210.71.9Head Face
%Collective dose
Person Sv
%Number millions
Per capita radiation dose from medicine has increased 560 percent
~3.0 mSv
20061980
0.54 mSv x 5.6 =
These results have not been reviewed and approved by Council.Not to be disseminated or referenced
Collective annual population dose from medicine has increased over 700 percent
880,000 person-Sv
20061980
124,000
Person Sv x 7.1 =
These results have not been reviewed and approved by Council.Not to be disseminated or referenced
Preliminary estimate of changes in
U. S. medical radiation exposure
Natural
3.0
CT scanning 1.5 mSv
Radiography 0.3 mSv
Nuclear medicine 0.8 mSv
All other ?? mSv
Medical ~3.0 mSv
Total ~ 6.0
Medical 0.54 mSv
Total 3.6 mSv per capita
Natural 2.8 mSv
U.S. 1980 U.S. 2006
Interventional 0.4 mSvAll other
2.4, 2.8, 3.0 mSv
Why does the value of natural background keep changing ….
even though in reality it has not changed for over 1 million years?
Ans: physicists
Preliminary estimate of changes in
U. S. medical radiation exposure
Natural
2.4 UNSCEAR
CT scanning 1.5 mSv
Radiography 0.3 mSv
Nuclear medicine 0.8 mSv
All other ?? mSv
Medical ~3.0 mSv
Total ~ 5.4
Medical 0.54 mSv
Total 3.6 mSv per capita
Natural 2.8 mSv
U.S. 1980 U.S. 2006
Interventional 0.4 mSvAll other
Computed tomography (CT scan)
Recent advances in machine technology have led to more applications and markedly increased usage
CT scans by year in US (millions)
18.3 19.521.0
22.625.1 26.3
30.6
34.9
39.6
45.4
50.1
53.9
57.6
62.0
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
No.
of
pro
ced
ure
s (m
illio
ns)
Annual growth of >10% per year
CT procedures by year (millions)
Annual growth > 10%/yr
U.S. population < 1%/yr
Preliminary Results for CT (U.S. 2006)
100438,00010067TOTAL
3.4154,73064.2Miscellaneous
12.856,00064.3CT Angiogram
0.151553.5Extremity
58254,0003825.4Abd/Pelvis
17.074,3001610.6Chest
8.738,0002819Head
%Collective dose person Sv
%Number
(millions)
75%
Effective dose per capita 1.46 mSv
Why has there been such spectacular growth in procedures ..
……..and such an increase in dose ??
Single slice CT scanner
Single detector
x-ray tube
Patient table
Tube rotates, image is obtained, then table moved incrementally and another tube rotation and another image obtained. Scan time ~ 10-20 minutes
Incremental motion
Helical (spiral) single slice CT scanner
Single detector
x-ray tube
Patient table
Constant table feed motion
Tube continuously rotates and table has constant feed. Scan time ~10-30 seconds
Multislice multidetector helical CT scanner
16-300 detectors
x-ray tube
Patient table
Constant motion
Constant tube rotation, constant table feed. More detectors.
Scan time 0.3-5 seconds. Now 300 slices/images in 0.3 second
CT scanning delivers high radiation doses
• “The absorbed dose to tissues from CT can often approach or exceed the levels known to increase the probability of cancer as shown in epidemiological studies” ICRP 2002
Unusual case of hair loss from excessive dose during CT angiograms
Is there a cancer risk from CT ?
1.0
1.1
1.2
1.3
1.4
100 200 300 400
Relative risk
1 CT scan sequence
3-phase CT liver scan
4-5% of CT scan patients
Organ dose (mSv)A-bomb data show a statistically significant increase at > 50 mSv
50
Comparison of effective doses
0.2 mSv
0.7 mSv
7 mSv
14 msv
x 350 =
x 20 =
New widespread uses of CT
• Clinical– Appendicitis– Renal colic/stones– Pulmonary embolism– Trauma
• Screening– Coronary arteries– Colonoscopy– Lung cancer
• Most of these improve confidence in diagnosis
• Few of these uses have been studied sufficiently to show a significant change in patient outcome
• They are clearly easy to interpret and fast to do
CT Use for Acute Appendicitis
• Typical clinical symptom triad absent in 50%
• Before CT~ 15-20% of operations resulted in removal of a normal appendix
• CT accuracy 97% and now only 3% of operations yield normal appendix
• CT has a higher accuracy for alternative diagnoses
Appendicitis
Normal
Abnormal
Renal stones/colic
Obstructing stone
Kidney
Dilated ureter
Bladder
Intravenous urogram (IVP)
Requires injection of intravenous contrast
Contrast reactions in 5% of patients
Death from contrast 1/40,000 to 1/100,000
Procedure takes 30 minutes
Dilated ureter4mm stone in distal ureter
Stranding and edema around kidney
CT scanning for renal colic
• Intravenous urogram rarely done anymore
• CT scan without intravenous contrast takes 30 seconds with an accuracy of 97%
• Effective radiation dose 14 mSv
• Repeated examinations common.
0
2
4
6
8
10
12
14
16
Effective dose (mSv)
Annual natural background
Annual public dose limit ICRP
1 Chest x-ray
1 Abdomen x-ray
1 Head CT
1 Chest CT
1 Abd/pelvis CT
Avg annual dose Chernobylcontam area 0-10 yr
Relative magnitude of individual doses
Many patients have more than CT examination
2002
2003
2004
2005
2004
This 35 year old had 18 CT exams
Nuclear medicine lung perfusion scan
Chest CT scan with intravenous contrast
Reduced blood flow to one lung- nonspecific
Large clot in right main pulmonary artery – clear diagnosis
CT scanning of the chest for pulmonary embolism
• Breast dose in thorax CT may be as much as 30-50 mGy, even though breasts are not the target of imaging procedure
• Breast dose from chest CT equals that from • about 10-15 sets of 2 view mammograms
• Often done on younger patients
• Now CT is routine for PE and in the U.S. has generally replaced nuclear medicine except for pregnant patients and those with contrast allergies
Trauma
With new multi-slice CT scanners, head, neck, chest abdomen and pelvis can be scanned in 10-30 seconds
Many significant findings are seen such as brain hemorrhage, small pneumothoraces and liver lacerations which are difficult or impossible to see on plain x-rays
Liver laceration
Small pneumothorax
0
5
10
15
20
25
30
35
Effective dose (mSv)
Annual natural background
Annual public dose limit ICRP
1 Chest x-ray
1 Abdomen x-ray
Trauma CT head>pelvis
Avg annual dose Chernobylcontam area 0-10 yr
Avg total 0-10 yr doseChernobyl contam area
Relative magnitude of individual doses
Coronary artery calcium scoring and screening
Calcified left anterior descending coronary artery
PA
Aorta
Coronary artery calcium scoring
• Calcification score is related to risk of future cardiac event
• But.. 50% of persons with myocardial infarct have “soft plaque” and no calcification
• Potential U.S. market > 50 million persons
• Radiation effective dose 3 mSv
• If used typically combined with other risk factors
• Not currently recommended for screening but it is still widely advertised and practiced in the U.S.
Coronary artery stenosis
Contrast invasive coronary angiogram 3-D CT scan
CT coronary angiography
• Really needs 64-slice CT scanner. 16-slice scanner is marginally adequate
• Not indicated for those needing bypass surgery
• Can be used to assess patency of grafts and stents
• Radiation effective dose 16 mSv
• Is now being used to examine patients with angina although value not proven
0
2
46
8
10
1214
16
18
Effective dose (mSv)
Annual natural background
Annual public dose limit ICRP
1 Chest x-ray
CT calcium scoring
CT coronary angio
Avg annual dose Chernobylcontam area 0-10 yr
Relative magnitude of individual doses
CT screening for lung cancer and followup of lung nodules
Nodules as small as 2-3 mm are easily seen on CT. On regular chest x-ray most non-calcified nodules need to be 8-10 mm to be reliably visualized
CT screening for lung cancer
• 70% of smokers have lung nodules
• < 0.1 % are cancer (< 1/1000)
• ~ 1-2 % nodule resection mortality• If surgery were done on 1000 nodules 10-20 deaths
might occur to find 1 cancer
• Do not rescan < 4mm nodules in low risk persons
• Scan at 3, 6, 12 and 24 months in others
• Radiation effective dose 7 mSv per scan
Is there really a benefit ??
•
Bach PB et.al. JAMA 2007
144 cancers found 44 expected
No reduction in mortality
38 deaths vs 38.8 expected
Henschke et.al. NEJM 2006CT scanning can prevent 80% of lung cancer deaths
JAMA March 7, 2007
0
1
2
3
4
5
6
7
8
Effective dose (mSv)
Annual natural background
Annual public dose limit ICRP
1 Chest x-ray
1 Abdomen x-ray
1 Chest CT
Avg annual dose Chernobylcontam area 0-10 yr
Relative magnitude of individual doses
CT (virtual) colonoscopy
CT scout image 3-D image of colon
Fiber-optic colonoscopy
CT virtual fly-through
CT colonoscopy screening
• Requires laxative preparation• Residual fecal material a problem
• Accuracy poor for lesions < 10 mm• Variability in interpretation
• Radiation effective dose 4-13 mSv
• 20-30% will be positive and need fiber-optic colonoscopy for biopsy
• Potential market in US 50+ million persons• Not yet widely used
0
2
4
6
8
10
12
Effective dose (mSv)
Annual natural background
Annual public dose limit ICRP
1 Chest x-ray
1 Abdomen x-ray
CT colonoscopy
Avg annual dose Chernobylcontam area 0-10 yr
Relative magnitude of individual doses
Incidental findings on CT scans
Gallstones~5%
Renal cysts
~50% older
Congenital
~5%
Fatty liver
~5-10%
Multiple Scan Average Dose
0%
5%
10%
15%
20%
25%
30%
0-10 10-20 20-30 30-40 40-50 50-60 60-70 70-80 80-90 90-100
>100
MSAD (mGy)
Frequency 2000-01 (n = 203)
1990 (n = 249)
S. Stern, USFDA
10-fold variation in CT scan doses
Isn’t the radiation risk lower because patients are older and don’t live as long ?
• Probably not much lower (maybe 35%)
• In the U.S. less than 5% of all examinations occur in the year prior to death
• A 65 year old has a 50/50 chance of making it to age 85
CT of the abdomen, pelvis, and chest: Age distribution, 2003Reweighted to be representative of US population age distribution
1.3%2.2%
3.7%
7.2%
12.4%
18.0%19.0% 19.4%
16.1%
0.7%
15.0%
10.1% 10.0%
13.7%15.3%
14.0%
9.6%
6.3%
4.4%
1.6%
0%
5%
10%
15%
20%
25%
Age 0-10 Age 11-17
Age 18-24
Age 25-34
Age 35-44
Age 45-54
Age 55-64
Age 65-74
Age 75-84
Age 85and
older
% of CTs % of population
CT scans of abdomen and pelvis
Exam distribution vs U.S. population
2003
Children are likely to be at 2-5x higher cancer risk from radiation than are adults. Adult CT technical factors are often used inappropriately on children
Nuclear medicine visits by year U.S.(millions)
10.2 10.5 10.9 11.8 12.6 13.5 14.5 14.9 15.7 16.5 17.2
0
5
10
15
20
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
Currently approximately 1 nuclear medicine procedure annually per 15 persons
5% Growth annually
Cardiac nuclear medicine
stress
rest
Ischemic area seen at stress fills in at rest
Cardiac nuclear medicine (wall motion)
Diastole Systole
Poor motion of inferior wall due to prior myocardial infarct
Cardiac nuclear medicine
• Techniques have been available for over a decade but number of procedures has almost doubled
• Cardiologists now own equipment and self-refer almost 2/3 of the cases
• New for-profit “Heart Hospitals” in almost every city in the U.S.
• Potential market > 50 million persons• Radiation effective dose 10 mSv
0
2
4
6
8
10
12
Effective dose (mSv)
Annual natural background
Annual public dose limit ICRP
1 Chest x-ray
1 Abdomen x-ray
Cardiac stress/rest perfusion
Avg annual dose Chernobylcontam area 0-10 yr
Avg total 0-10 yr doseChernobyl contam area
Relative magnitude of individual doses
Combined CT and other modalities
Post colon cancer surgery Rising tumor marker (CEA)
Positron emission (PET) scan
Bladder
Kidneys
Heart
18F-FDG
fluorodeoxyglucose
R L
Combined PET/CT scan
Lung metastasis from laryngeal cancer
CT scan PET/ CT scan
Nodules must be > 8 mm to be reliably visualized
What is the effective dose from one PET/CT scan?
740 MBq 18F-FDG 14 mSv
Head CT 2 mSv
Neck CT 3 mSv
Chest CT 7 mSv
Abdomen CT 8 mSv
Pelvis CT 6 mSv
Total 40 mSv
0
5
1015
20
25
3035
40
45
Effective dose (mSv)
Annual natural background
Annual public dose limit ICRP
1 Chest x-ray
1 Abdomen x-ray
Whole body PET/CT
Avg annual dose Chernobylcontam area 0-10 yr
Avg total 0-10 yr doseChernobyl contam area
Relative magnitude of individual doses
So how big is 880,000 person-Sv ?
880,000 person-Sv880,000
Collective population doses: Comparison
• ~400,000 person-Sv worldwide over all time from entire Chernobyl release*
• ~880,000 person-Sv annually from radiology and nuclear medicine in U.S.
• ~900,000 person-Sv annually from natural background radiation (assuming old NCRP 100 calculations)
* UNSCEAR 2007
Is there any potential detriment from 880,000 person-Sv ?
Depends who you talk to…..
… but the answer is “yes” for all of medicine if you subscribe to LNT hypothesis
… and yes for multiple CT or NM scans regardless of your LNT beliefs
Does anybody, or should anybody, regulate this,
the largest (and controllable) source of radiation exposure ?
The largest radiation source in the U.S. remains largely unregulated and appears likely to continue to grow with minimal constraints
Manufacturers are now advertising directly to self-referring clinicians
http://www.jeffxray.com/handler.cfm?event=practice,template&cpid=10192
Gift Certificates for Radiation Exposure ????
How does the typical physician view radiation protection ?
How bad is the patient bleeding ?
Will the test or therapy affect outcome ?
Is it available ?
What is my experience ?
What is the downside if I don’t order it ?
Have I seen anything in the literature lately?
What is my gut feeling ?
Radiation risk ?? Is that an issue ??
My observations
• Have we substantially increased the dose medical diagnostic uses of radiation? Absolutely ~ 500 – 700 percent
• There is no question that serial CT and NM doses are in the range known to increase the probability of cancer
• Do we think we are practicing better medicine ? Yes
My observations
• Is there a radiation risk from these procedures? Probably (low individual risk but possibly large numbers)
• Do most physicians have any idea of the magnitude of increased medical radiation dose or possible risk? Definitely not
• Have we really shown an evidence-based benefit for any these procedures ? Certainly not for most
My observations
• Do most physicians have any idea of the magnitude of increased medical radiation dose or possible risk? Definitely not
• Can these doses be substantially reduced without losing diagnostic accuracy? Absolutely
• Remember: medical radiation usually has direct benefit to individual. We must be careful not to eliminate needed exams
Are we safer ?Is all this justified ??
You decide
Thank you